Field of the Invention
The present invention relates to an image reading apparatus capable of reading an image described in an original by specifying a size, and an image forming apparatus including the image reading apparatus.
Description of the Related Art
In an image reading apparatus, such as a copying machine, the following scanning action is typically performed. The so-called auto original conveying portion continuously conveys originals to be read one by one. After that, images are optically read from these originals and then image data is acquired.
When an original fed by an automatic document feeder portion is read, a size of the original is sometimes detected on a tray on which a sheaf of originals is disposed, and then an image region with the size that has been detected is read. Using the size of the original detected on the tray, can progress processing, such as determination of a sheet size to be fed from a printer. Accordingly, productivity of the number of sheets to be read per hour or a first copy output time (FCOT) during which a printing action starts and a first sheet is discharged, can be improved.
However, the size of the original detected on the tray and a size of the original that has been conveyed and read are sometimes different from each other. For example, this is a case where a plurality of different original sizes is mixed and disposed (consolidation). In this case, when a user specifies an image reading size, a case where a reading region of the original with respect to the size specified by the user is different from a reading region of the original determined with an actual, correct original size, sometimes occurs.
When reading continues in this state, there is a risk that the correct reading region is not read and a reading image of the original becomes partially lost with respect to the initial original. In a worst-case, there is a risk that the reading region does not completely correspond to the original region so that the reading region becomes a blank paper.
The following configuration has been proposed with respect to this type of abnormality of the reading image. An abnormality determining unit determines an abnormal value. In a case where abnormality is detected, a reading position is changed (refer to Japanese Patent No. 3313098).
In addition, the following configuration has been proposed. In order to reduce a possibility that a reading image becomes partially lost, the length of an original that has been being conveyed, in a conveying direction is measured. Then, an image size is switched and reading is performed (refer to Japanese Patent Laid-Open No. 2000-155444).
As described above, in a case where the user has specified the image reading size, the following state occurs. The reading region of the original with respect to the size specified by the user and the reading region of the original determined with the original size that has been actually conveyed, are different from each other. In this case, the configuration in which the abnormality determining unit changes the reading position in a case where abnormality is detected as in Japanese Patent No. 3313098 or the configuration in which the length of the original is measured in a conveying direction, the image size is switched, and the reading is performed as in Japanese Patent Laid-Open No. 2000-155444, cannot determine a sheet size fed from a printer. Therefore, there is a risk that productivity and a FCOT degrade. That is there is a problem that a deficiency of the image cannot be prevented with the productivity and the FCOT prevented from degrading.
Here, even in a case where the reading region specified by the user and the region of the original are different from each other, a deficiency of an image does not occurs in a case where a region larger than the actual original size is specified as an image reading size. In a case where the deficiency of an image does not occur, carelessly cancelling the reading of the original causes non-ease of use.